1. Field of the Invention
The present invention relates to containers for packaging and more particularly relates to side-by-side detachably connected container strips and methods of making them.
2. The Prior Art
The packaging industry has developed a variety of so-called "form and fill" machines.
These machines are designed for use with products which are made and sold in high volumes. Such machines form a container from a web or webs of material, insert the product into the container to fill it and then seal the container to provide a finished package.
When products are made and sold in relatively low volume the complex and relatively expensive form-and-fill machines are uneconomic. While various mechanical aids have been developed, the loading and sealing steps involved in packaging low-volume products have been performed, at least in part, manually.
The developing of chains of open bags such as those shown and described in U.S. Pat. No. 3,254,828 entitled "Flexible Container Strips" and issued to Hershey Lerner presaged a system of packaging which is well suited to relatively low-volume applications. In its most popular form, this system uses a dispensing machine which carries a rolled web of connected and open bags. The bags are fed, closed end first, through a dispensing opening. As each bag emerges from the opening, a concurrent flow of air through the opening inflates the bag. The product to be packaged is inserted into the bag. Subsequently, the bag is both sealed to form a container and separated from the web.
Dispensing and sealing machines have been developed which automatically feed the bags sequentially to a station where they are loaded. Once each bag is loaded, the machine seals the bag and severs it from the web as a finished package. One such machine is disclosed in U.S. Pat. No. 3,815,318 issued on June 11, 1974 to Bernard Lerner entitled "Packaging Method and Apparatus". This machine may be coupled to automatic counting and loading equipment too for efficiently and automatically packaging products which are made in moderate volumes.
The dispensing and sealing machines have generally been constructed so that it is mechanically possible to feed side-by-side container strips through the machine simultaneously from a strip storage location to loading and sealing stations. Concurrent feeding of a plurality of strips has the desirable effect of multiplying the machine's capacity. While this effect is desirable, it has not, as a practical matter, been achieved in the past.
Simultaneous feeding, loading and sealing of side-by-side container strips has not been practical in the past because of the nature of the plastic material from which the strips are made. Normally, container strips are formed from a heat-sealable plastic material, such as polyethylene, which has a tendency to yieldably stretch during container strip forming process.
Slight stretching of the material is extremely difficult to avoid during the forming processes and the result is that slight dimensional errors in the length of individual container portions are created as the material is fed through strip-forming apparatus. The dimensional error introduced in an individual container portion is of negligible consequence so far as the affected container portion itself is concerned, but these individual errors accumulate over the length of the container strip. If a dimensional error of 0.001 inch is present in each container portion of a container strip having 3000 container portions, the last container portion of the strip is offset 3 inches along the web from where it should theoretically be located.
When a single container strip is fed through one of the described dispensing and loading machines, a cumulative effect of dimensional errors is avoided by controlling the strip feed in response to sensing successive container portion locations along the strip. However, if side-by-side container strips are simultaneously fed through this machine, extremely small differences in dimension of container portions of one strip relative to the dimensions of container portions of another strip produce a cumulative error resulting in the container strips being moved out of registry with each other rather promptly. For example, if each container portion of the adjacent container strip, simultaneously feeding one thousand container portions of side-by-side strips to the loading station will result in an accumulated one inch difference between corresponding load openings of the strips. This has precluded simultaneously loading and sealing container portions of side-by-side container strips with the described loading and sealing machines.
The prior art has proposed no practical solution to the problem of how to concurrently supply container strips while maintaining registration. Utilization of the known art results in either or both the dispensing and sealing machines being extensively modified, or the finished package being unattractive in appearance, and perhaps other standpoints.